Electric arc lamp



' Jan. 1, 1924 1,479,370

, L. R. COFFIN ET AL ELECTRI C ARC LAMP Filed June 8. 1917 3Sheets-Sheet 1 Figi . 1N VEN ToRs f awr Jan. l y

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ELECTRIC ARC LAMP Filed June 8, 1917 3 SheetsSheet 2 N @EN TORS w Q91,"

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l such as are especially adapta le for use inA which will o eratesuccessfully with the useA harina Jui. 1, i924.

' UNITED s'rATEs LESLIE n..I corm, or Eminem, wAsHINc'i'oN,4 im nEUnENw. ins'ncx, n.,

i 1,419,310 PATENT oFEicE. i

0F SAN FRANCISCO, CALIFORNIA.

ELECTRIC ABC2v LAMP.

Application led June 8,

State of Washington, and REUBEN. W. MAs- Tron, Jr., a citizen of theUnited States, and

' a resident of San Francisco, in the county of San Franciscoand Stateof California, have invented certain new and useful Improvements inElectric Arc Lamps; and we do hereby declare the .followin to be a full, clear, and exact descri tion o the invention, such as will enableot ers skilled in the art to which it appertains to make and use thesame.

, This invention vrelates to improvements in electric arc lamps and morearticularly to c inematographic, stereopticon or other pro- "jectingpurposes.

One object of the presentinvention is to provide a projector type ofelectric arc lamp of a single-p ase alternating current of commercial fruency without necessity for the use of auxi iary rectifying a paratus,and which 'may also be successi ly and accurately operated with the useof unidirectional electric currents.

A further object is to provide, in an arc lamp of the ty specified,simple and efficient means w ere y' the three electrodes employed, maybe quickly and accurately adjusted with relation to each other and.relatively to the projector lens.

A further object is to so arrange the elec trodes and circuits of anelectric arc lamp as to facilitate such rectification of the currentemployed as can obtain incident to theaction of the arcs at thecooperating electrode terminals.

With these and other objectsin view, the invention consists in certainnovel features of construction and combinations of parts and circuits ashereinafter set forth and pointed out in the claims. I y

In the accompanying drawings; Figure 1 is a diagrammatical view showing'the arrangement of electrodes and circuits when the lamp is employedwithA unidirectional currents; Figure 2 is a diagrammatical view showingthe adaptation of the lamp for sin;

gle-phase alternating currents; Fi res 3 and 4 are views, partly inelevation an partly in section, of a lamp embodying the invention;

1917. Serial I0. 178,588.

Figure 5 is a fragmentary sectional view showing the hinge connectionbetween the rents, an arrangement of three electrodes is provided so asto obtain a plurality of arcs, two of said electrodes being connectedreslpectively vby leads to the end terminalsof t e secondary winding ofa single-phase alternatin current supply transformer, and

the-thir to the neutral or mid-point of said secondary windnv of thesingle-phase su ply transformer. eactance coils of suitable constantsmay be laced in circuit with the leads connecting t e three electrodesof the lamp to the secondary winding of the singlephase supplytransformer, for the urpose of. regulating and maintaining the p uraltyof arcs between said-electrodes..

' In the alternating current operation of the lamp, partialrectification of the alter.

nating current supplied takes` lace. Hence the arcs produced in thethree e ectrod'e lamp with alternating current areboth unidirectionaland alternating in character. When a proper overlapping of thesuccessive half waves of current be produced, the rectifying actionwhich obtains exerts a steadying influence on the plurality of arcsbetween the lcooperating electrodes.

The three electrodes are so arranged as to converge toward a common ointand in addition to separate 'means ofp adjustment for the electrodesindividually, a pantog'raphic structure is employed to obtain asimultaneous movement of the three electrodes toward the common oint ofconvergence by the manipulation o one controllin rod. The advantage ofan organization o this sort lies in the fact that the arc is alwaysmaintained at a sensibly constant distance .from the projector lens.This will be readily understood when consideration is gilven to the factthat as the arcsburn and t e yelectrodes wear away, thus increasing boththe distance from .the arcs to the projector lens and the arc-gapsbetween electrodes, a slight adjustment of the pantographic controlr'eadjusts the arc separation between electrodes, and hence immediatelyrestores the arc to its original position with respect tothe projectorlens.

Referring to Figure 1, 1, three carbon electrodes, the former of whichare connected respectively through two resistances 4, 5 toa common point7, which is the negative terminal of the direct current supply circuit.The third or central carbon 3 is connected with the positive terminal 6of the direct current supply circuit. The three electrode arrangementresults in the plurality of arcs being localized and forming a very hot"crater at the positive electrode 3, givlng a greater.. luminousintensity than is obtainable With the ordinary/two electrode type ofarc-lamp. In addition, the arc is rendered very steady and requireslittle attention or adjustment, a feature of much importance incinematograph apparatus.

In Fi re 2, 1, carbon e ectrodes, connected through respectively, topoints 2, 3 represent the three two reactance coils 4,'5 8, 9,representing the outer ends of the secondary winding of av single-phasealternating current 'supply transformer 9. The third carbon electrode 3is connected through a reactance coil 6* to the mid-point 7*? of thesecondary winding 8, 9 of the single-phase alternating current supplytransformer. When thev singlephase alternating current supplytransformerjis remote to the lamp, the neutral point 7 of thesingle-phase circuit may be obtained by. providing two balanced react--ances disposed in series and bridged across the circuit at a pointcorresponding to 8,A 9. The reactance coils 4, 5 are inserted to providean overlappin of successive half-waves of current essentia to thecontinued excitation of the arc. The characteristics of these reactancecoils are not. specifically given, since they are determined by therequiredv angle of overlap of the currents of successive half Wavesnecessary to give the desired stability together with. other factorswhich will vary w1th the capacity and usage of the lamp. Reactance coil6 of required characteristics is inserted in circuit between the points3 and 7a to maintain the voltage in said circuit above the counter E. M.F. of the arcs. With this arrangement, the alternatin current suppliedis 1n part rectified and t e arcs are formed solely by successive halfvwaves of current, between electrodes 1., 3 and 2, 3 respectively areunidirectional.

The arcs occurring from electrodes 1 by 3 to 2 and 2 by 3 to 1 arealternating in charvided circuits indicated by 3, 6

2, 3 represent rieddby the former of which are acter. The rectified partof the alternating current supplied,-therefore, exists in the diand 7./Owing to the high temperature of the carbon-arc and its consequent lowvoltage range of rectification, a complete rectification of' thealternating current cannot4 take place such as would be possible withelectrodes of lower temperature boiling points.

Electrode 3 is smaller than either electrodes 1 or 2 which fact`promotes high incandescence of said electrode d'ue to the passage of thearcs from 1 by 3 to 2 and from 2 y 3 to 1 in the case of alternatingcomponents of the arc current and from 1 to 3 and 2 to'3 respectively inthe'case of the unidirectional component of the arc current. In the lampshown in Figure 3, electrodes 1 and 2 are supported respectively byholders 4b and 5" carried by arms 6b and 7 b, the lutter being supportedby the carriers 8'J and Jb Iwhich are in turn supported by thepantographic structure 10,11, 12 and 13. The electrode 3 is sup A arm15, w ich is supported in the carrier 16, the latter being pivoted onthe pantograph arms 12 and 13. In addition to being pivoted on thepantograph arms 12 and 13, the carrier 16 slides in a slot on the base17. The two-arms 10 and 11 of the pantograph are pivoted to a block .18which orted byvholder 14 caralso slides in vla slot on the base 17 Theblock 18 is driven by the threaded I'Od 19. swiveled in a block 2()rigidly attached to the base 17 The upper and lower junctions ofthepantogjraph arms 10, 12 and 11, 13 are pivoted y axles 21 and 22passing through each pair and a slot 21b in the carriers 8* an 9brespectively and thence extending into the slotted upright guides 21 and22'L (see Figures 3 and 4). Thus-lateral v movement of the upper andlower pantograph arm junctions is restrained, and hence operation of therod 19-causes a recession or approach of the carriers 8b and 9", andtherefore, also, of the electrodes 1 and 2. By reason of the pantographarms 12 and 13 being pivoted to the carrier 16 which is guided Aon thebase 17, va recession or approa h of the'carrier 16 is caused andtherefore,

also of the electrode 3. v Thus operation of the rod 19 causescontemporaneously and associated carriers, arms,.holders, etc.,

above described, is rigidly attached to a shaft 23 movable vertically ina' holder by means of a rack and pinion gearing 25-26 controlled by amanually operable rod 27. The holder 24 is arranged to slide on twoparallel rods 28, 29 usually provided in the lamp cabinet associatedwlth commercial cinematographic machines.

Theelectrode holders 4", 5b and 14 are in- J able rod 41,

yby means of the bevel 7l* and 32 resulated from their carrying arms 6",15 by the insulatedjoints 30, 3l and spectivel'y, and in addition, pivotjoints' 33, 34 and 35 are provided between said insulated joints and theelectrode holders 4", 5" and 14 by which means additional an laradjustments of the three electrodes wit respect to one another can bemade, if desired. he upper carrier 8b is made of two parts, the lowerpart being attached to the pantographic structure 10, 11, 12 and 13 inthe manner previously described. The upperpart is hollow so that the arm6b which supports the electrode holder 4b be caused to move axiallyforward or bac independently of the carrier 8h as operated by rod 19, byrotation of a threaded rod 36 swiveled in the u per part of the carrier8b and entering a t readed socket in the arm 6". Moreover the upper partof the carrier 8* is hinged at or near one end to the lower by a pivotpin w andA part of said carrier 8b ar and screw jack arrangement, 37, zdby the manually opera le rod 38, can be caused to tilt up or down at oneend, thereby raising or lower` ing the arm 6h and, therefore, also theelectrode 1. Rigidly attached to the arm 6 is a spur gear 39 whichmeshes with another spur gear 40 attached rigidlyto a manuallyoperresting in bearings attached to the upper. art of the carrier 8b,which can cause a ra ial movement of the arm 6b with respect to itsaxis, and hence also cause a radial movement of the electrode 1. l Acollar 42 is provided on the spur gear 39 which fits about the spur gear40 so that the two gears remain meshed regardless of the positionaxially, of the arm 6" controlled by the rod 36. l

The lower carrier 9" piece attached is constructed in one 10, 11 12 and13 as previously described, and is hollow so that the arm' 7b whichsupports the electrode holder 5b and electrode 2 may be caused to moveaxially forward or back independently of the carrier as operated by rod19, by rotation of the threaded rod 43 swiveled in the carrier 9" andentering a threaded socket -in the arm 7.

The central carrier 16 the arm 15 which supports the electrode holder 14and electrode 3 may be caused to move axially forward or backindependently of the carrier 16, 'asoperated by rod 19, by rotationofthe threaded rod 44 swiveled 1n thesaid carrier 16 and enterinv athreaded socket in the arm 15. The threa ed rod 44 in this case ssesthrough and is supported by the threadgd rod 19.

The lamp and its electrodes will in all cases be adjustable with respectto the lens of the projecting apparatus, said lens bein showndiagrammatlcally in Figure 3 and 45.

and` electrode 1 mayI to the pantographic structure is hollow so that`While we have particularly described and illustrated the bestembodiments of our invention which are now known to us, it will bereadily understood that many changes can be made in the form of ourinvention without departin from its spirit.

aving` fu y described our invention what we claim as new and desire tosecure by Letters Patent, is

1. .In a projector type of arc-lamp,

electrodes axially towardl and away from the j lens.

2. An arc-lam for cinematographic, stereopticonv or ot er projectionpurposes comprising a panto raphic structure as a supporting means, tree electrode carriers swun thereon, one being intermediate of the ot ertwo and slidin 1n a fixed support, electrodes mounted in said carriers,the outer electrodes converging toward the central electrode whereb aplurality ofarcs may be formed simu taneously, guides controllingthedirection of movement of the members of the pantographic structure andmeans for controlling the movement of the pantographic structure,electrode carriers, and therefore, also the three electrodessimultaneously, so that the latter will converge towar outer electrodeswith two ter- LESLIE R. COFFIN. REUBEN W. MASTICK, JR.

Witnesses to signature of Leslie R. Collin:

N Noms, C. W. HOWARD. Witnesses to the signature of Reuben W.

astick, `r.: y R. T. lfoams, Gnonon W. SENGER,

s'ource of single phase alternat-

